Nickel Plating

Nickel is a silver-white metal generally used to enhance the value, utility, and lifespan of industrial equipment and components by protecting them from corrosion. Nickel is also commonly used in the chemical and food processing industries to prevent iron contamination. Because the properties of nickel can be controlled and varied over broad ranges, there are numerous applications for nickel plating, including ...

• Corrosion prevention
  
  
• Controlling lubricity
  
  
• Controlling hardness
  
  
• Magnetic properties
  
  
• Controlling reflectivity
  
  
• Controlling emissivity
  
  
• Controlling absorptivity

Nu-Metal Finishing offers a wide variety of nickel surface finishes. These fall into the major categories of electrolytic (or electro-plated) and electroless. One of our processes is sure to be ideal for your application.

Electrolytic Nickel Electrolytic nickel is electro-plated, and can be deposited soft or hard, dull or bright. Hardness can range from 150-500 Vickers. Appearance can range from a dull grey to an almost white, bright finish. Nu-Metal Finishing offers a wide range of electroplated nickel coatings.

Sulfamate nickel is deposited from a nickel sulfamate bath, and is the most widely used electrolytic nickel. It is often used as a final plating layer and also as an underplate for precious metals. Sulfamate nickel is a pure deposit that allows soldering and brazing during later assembly steps. It is normally a dull grey to dull silver color depending upon the finish of the plated part.

Watts nickel is deposited from a nickel sulfate bath. Watts nickel normally yields a brighter finish than does sulfamate nickel since even the dull Watts bath contains a grain refiner to improve the deposit. Watts nickel may also be deposited as a semi-bright finish. Semi-bright Watts nickel achieves a brighter deposit because the bath contains organic and/or metallic brighteners. The brighteners in Watts baths levelize the deposit yielding a smoother surface than the underlying part. The semi-bright Watts deposit is easily polished to a high lustre; however, the brighteners may lead to problems with soldering and brazing, and this should be considered when selecting a finish for your application.

A bright nickel bath contains a higher concentration of organic brighteners which have a levelizing effect on the deposit. Sulfur-based brighteners are normally used to achieve levelizing in the early deposits and a sulphur-free organic, such as formaldehyde, is used to achieve a fully bright deposit as the plating layer thickens. Organic brighteners yield a lustrous deposit; however, the negative effects on later assembly operations such as brazing and soldering should be considered.

Black nickel is a decorative coating that is often applied over an underplating of electrolytic or electroless nickel. Black nickel offers little in the way of additional protection, and is easily scratched or stained. A thin layer of black nickel gives an attractive cosmetic finish. Thicker layers of black nickel attain a matte black finish that is often used to achieve high emissivity in aerospace applications.

Electroless Nickel Electroless nickel plating is an autocatalytic process and does not use externally applied electric current to produce the deposit. The electroless process deposits a uniform coating of metal, regardless of the shape of the part or its surface irregularities; therefore, it overcomes one of the major drawbacks of electroplating – the variation in plating thickness that results from the variation in current density caused by the geometry of the plated part and its relationship to the plating anode. An electroless plating solution produces a deposit wherever it contacts a properly prepared surface, without the need for conforming anodes and complicated fixturing. Since the chemical bath maintains a uniform deposition rate, the plater can precisely control deposit thickness simply by controlling immersion time.

Nu-Metal Finishing offers five electroless nickel plating types ideally suited to a wide variety of applications.

Low-phosphorus electroless nickel yields the brightest and hardest deposits. Hardness ranges from 60-70 RC. Low-phosphorus content improves soldering and brazing performance. Nu-Metal's low-phosphorus electroless nickel plating conforms to ASTM 733 B, Type III, and MIL-C-26074 as described in the specification summary.

Medium-phosphorus or mid-phos is the most widely used electroless nickel bath. If phosphorus content is not specified, mid-phos will likely be chosen by the finisher. The hardness is typically 40 RC. Porosity is lower, and conversely corrosion resistance is higher than low-phos electroless nickel. Nu-Metal's mid-phosphorus electroless nickel plating conforms to ASTM 733 B, Type IV, and MIL-C-26074 as described in the specification summary.

High-phosphorous electroless nickel is dense and dull in comparison to the mid- and low-phosphorus deposits. High-phosphorus exhibits the best corrosion resistance of the electroless nickel family; however, the deposit is not as hard as the lower phosphorus content. Hardness may be improved by heat treating. High-phosphorus is a virtually non-magnetic coating. Nu-Metal's high-phosphorus electroless nickel plating conforms to ASTM 733 B, Type V and MIL-C-26074 as described in the specification summary.

Nu-Metal Finishing also offers two additional types of electroless nickel for specialty applications. Nickel boron is often used as an underplate for metals that require firing for adhesion. Nickel PTFE composite or nickel-Teflon® is used for lubricity, particularly in UHV environments.

For more information on Nu-Metal Finishing's electroless and electrolytic nickel plating, or for help on specification callouts, contact us at 1.800.303.1050 or email us today.

Specifications Summary

AMS-QQ-N-290
covers electrolytic nickel plating on various metals.

Sample callouts:
Nickel Plate per QQ-N-290, Class 2, 400 µin
Nickel Plate per QQ-N-290, Class 2, Grade F
Nickel Plate per QQ-N-290, Class 1, Grade F, SD

It is preferable to specify thickness directly (in mils, µm or µin). See website pages on Nickel Processes for more information on single vs. multilayer and bright vs. dull deposits. Nu-Metal offers this process with or without CoC.

AMS 2403 covers electrolytic (sulfamate bath) nickel plating on various metals.

Sample callouts:
Nickel Plate per AMS 2403, 500 µin

There are no types, classes or other categories specified. Thickness is specified directly (in mils, µm or µin). Nu-Metal offers this process with or without CoC.

MIL-P-18317 covers black electrolytic nickel plating on various metals.

Sample callouts:
Nickel Plate per MIL-P-18317, Low Emissivity

There are no types, classes or other categories specified. It is helpful to callout either "Cosmetic" or "Low Emissivity" to give some quidance on the application. Nu-Metal offers this process with or without CoC.